Recently there has been increasing interest in the field of biodegradable polymers. Such polymers have been used in medical and pharmaceutical applications in the past. Typically, such polymers are polymers of one or more of lactic acid, glycolic acid, hydroxy butyric acid and hydroxy valeric acid. These type of polymers arc of interest as they degrade to "naturally" occurring by products and they arc degraded by microbes in the natural environment. Additionally as the polymers are esters they may be hydrolysed under relatively mild conditions.
WO 90/01521 published Feb. 22, 1990 discusses the lactide polymers. The patent application proposes using this type of polymer in commodity plastic applications such as molded products. The patent application does not disclose using the polymers as a binder for or in fibrous webs.
Imperial Chemical Industries PLC (ICI) have a significant patent portfolio in the field of hydroxy alkanoates such as copolymers of hydroxy butyrate and hydroxy valerate, sometimes referred to as PHBV. ICI have proposed that such polymers could be used in injection molding applications for household wares such as containers and the like. U.S. Pat. Nos. 4,477,654 issued Oct. 16, 1984; 4,910,145 issued Mar. 20, 1990; 4,391,766 issued Jul. 5, 1983; 4,360,488 issued Nov. 23, 1982; and 4,360,583 issued Nov. 9, 1982 are representative of the ICI patents. These patents relate to processes for the production of poly hydroxy butyric acid (PHB) or copolymers of hydroxy butyric acid and hydroxy valeric acid (PHBV) by growing a microorganism, extracting the polymer from the microorganism and molding the polymer. However, the patents do not suggest using the polymer as a binder in a fibrous web.